Influence of aerosol hygroscopicity and mixing state on aerosol optical properties in the Pearl River Delta region, China.

/pdf/effects-of-aerosols-on-solar-radiation-in-the-aladin-hirlam-14wg7m1gbb.pdf

Effects of aerosols on solar radiation in the ALADIN-HIRLAM NWP system

Haze can cause serious atmospheric pollution affecting air quality, human health and even global climate. In order to investigate aerosol columnar size distribution and water uptake during haze evolution, we analyse ground-based observations during an extreme winter pollution case at Beijing on 12 January 2013 (haze day) as compared to those registered on 9 January (non-haze day). We study the evolution of the aerosol size distribution using retrievals from a ground-based CIMEL sun-sky radiometer of the Aerosol Robotic Network (AERONET). Our results show that while the hourly volume growth rate of a sub-micron fine mode presented in the size distribution remains below 0.010 mu m(3)/mu m(2)/hr during the non-haze day, it can rapidly increase during haze pollution event, reaching a maximum value of 0.075 mu m(3)/mu m(2)/hr. The mean size of fine mode particles becomes larger during the pollution event, while it is reduced for coarse mode particles. The mean volume of water uptake is 0.013 mu m(3)/mu m(2) in haze day, being about 13 times larger than that in non-haze day. Meanwhile, the volume of water-soluble inorganic aerosols increases from 0.036 to 0.298 mu m(3)/mu m(2), partly explained by the increase of water uptake during the haze event and also likely by accumulation of particle matters due to stagnating atmospheric conditions. The increase of water-soluble particle volume, which is enhanced by water uptake, significantly contributes to haze evolution.

/pdf/aerosol-column-size-distribution-and-water-uptake-observed-51azzkhs0v.pdf

Aerosol Column Size Distribution and Water Uptake Observed during a Major Haze Outbreak over Beijing on January 2013

Handan has been one of the most polluted cities in China since 2013 and became the top city for PM2.5 in 2017. In this research, we observed coarse particulate matter (PM10), fine particulate matter (PM2.5), submicron particulate matter (PM1), and the chemical composition of PM2.5 from November 16, 2015, till March 14, 2016, in Handan. During the observation period, hourly concentrations of PM10, PM2.5, and PM1 peaked at 1070.1, 864.4, and 519.5 µg m–3, respectively. Severe pollution occurred on a large fraction of days in the heating season, which was characterized by frequent and long-lasting pollution episodes. A large fraction of the transport trajectories during nine typical episodes during that period in Handan were from the northwest. Water-soluble ions (sulfate, nitrate, and ammonium) in PM2.5 accounted for the largest proportion at all pollution levels. The highest proportion of SIA occurred in a heavily polluted episode, during which it was as high as 50.0% (sulfate: 18.8%, nitrate: 18.7%, and ammonium: 12.5%). The sulfate and ammonium in PM2.5 increased gradually while the nitrate decreased as the level of pollution rose from clean to heavily polluted. The fraction of SOA and OM to PM2.5 decreased as the pollution level increased, indicating a weakening of photochemical reactions. The POA in PM2.5 increased with the aggravation of haze, and the heterogeneous chemistry was enhanced by the aggravation of pollution. Liquid reactions were important in the formation of sulfate during pollution and non-pollution stages. Liquid reactions of NO2 are enhanced in the pollution stage during the heating season in Handan.

/pdf/evolution-of-key-chemical-components-in-pm2-5-and-potential-2nrn63zemi.pdf

Evolution of Key Chemical Components in PM2.5 and Potential Formation Mechanisms of Serious Haze Events in Handan, China

Relative Humidity Dependence of Aerosol Optical Properties and Direct Radiative Forcing in the Surface Boundary Layer of Southeastern China

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Relative Humidity Dependence of Aerosol Optical Properties and Direct Radiative Forcing in the Surface Boundary Layer of Southeastern China